Business segment data (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Segment Reporting Information [Line Items]
Revenues	$ 42,188	$ 37,138
Total revenues	43,867	38,147
Earnings before income taxes from operating businesses	5,885	4,338
Total earnings before income taxes	7,295	4,931
Geico [Member]
Segment Reporting Information [Line Items]
Premiums earned	4,399	4,016
Earnings before income taxes from operating businesses	266	124
General Re [Member]
Segment Reporting Information [Line Items]
Premiums earned	1,469	1,471
Earnings before income taxes from operating businesses	95	81
Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	2,796	2,071
Earnings before income taxes from operating businesses	974	(191)
Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	713	507
Earnings before income taxes from operating businesses	54	71
Berkshire Hathaway Insurance Group Investment Income [Member]
Segment Reporting Information [Line Items]
Interest, dividend and other investment income	1,001	1,056
Earnings before income taxes from operating businesses	996	1,052
Berkshire Hathaway Insurance Group [Member]
Segment Reporting Information [Line Items]
Revenues	10,378	9,121
Earnings before income taxes from operating businesses	2,385	1,137
BNSF [Member]
Segment Reporting Information [Line Items]
Revenues	5,284	5,002
Earnings before income taxes from operating businesses	1,289	1,115
Finance and Financial Products Reportable Segment [Member]
Segment Reporting Information [Line Items]
Revenues	950	959
Earnings before income taxes from operating businesses	169	163
Marmon [Member]
Segment Reporting Information [Line Items]
Revenues	1,730	1,793
Earnings before income taxes from operating businesses	266	269
McLane Company [Member]
Segment Reporting Information [Line Items]
Revenues	10,785	8,073
Earnings before income taxes from operating businesses	132	102
MidAmerican [Member]
Segment Reporting Information [Line Items]
Revenues	3,116	2,894
Earnings before income taxes from operating businesses	553	483
Other Businesses [Member]
Segment Reporting Information [Line Items]
Revenues	9,945	9,296
Earnings before income taxes from operating businesses	1,091	1,069
Not Allocated to Segments [Member]
Segment Reporting Information [Line Items]
Investment and derivative gains/losses	1,711	896
Interest expense	(72)	(66)
Intersegment Eliminations and Other Reconciling Items [Member]
Segment Reporting Information [Line Items]
Total revenues	(32)	113
Earnings before income taxes from operating businesses	$ (229)	$ (237)